"Jason Richwine let us know he’s decided to resign from his position. He’s no longer employed by Heritage," spokesman Daniel Woltornist said in an email to HuffPost. "It is our long-standing policy not to discuss internal personnel matters."

The report put the cost of immigration reform at a whopping $6.3 trillion. Though Heritage's 2007 report was one of the reasons an earlier immigration bill failed, the 2013 report was widely mocked, even by Republicans the foundation hoped would support it.

"Superior performance on basic economic indicators is to be expected from later generations, who go to American schools, learn English, and become better acquainted with the culture," he wrote. "Despite built-in advantages, too many Hispanic natives are not adhering to standards of behavior that separate middle and working class neighborhoods from the barrio."

"There can be little dispute that post 1965-immigration has brought a larger and increasingly visible Hispanic underclass to the United States, yet the underlying reasons for its existence cannot be understood without considering IQ," he wrote.

He argued that these individuals were more likely to accept government benefits. "When given the choice between a paycheck from a low-paying job and a welfare check, most intelligent people would realize that the welfare check offers them no potential for advancement. Low-IQ people do not internalize that fact nearly as well," he wrote.

Heritage sought to distance itself from the dissertation, saying it did not reflect the group's positions.